Windmills and water mills have been used for centuries to pump water or to power a wide range of mechanical devices. Over the past century both have become important means of electrical power generation.
In recent years there has been considerable effort expended to improve the efficiency of wind and water turbines used for electrical power generation with a view to reducing dependence on non-renewable resources. Significant expansion of the power generating capacity of such wind and water turbines will however be highly dependent on improvements in existing technology. This is due to the fact that “prime sites” for wind and water turbines, which have comparatively high mean energy flows and are in reasonable proximity to roads and power grids, are becoming scarce. As a consequence, it is widely recognized that if projected future increases in the power generation capacity of wind and water turbines are to be met, current technologies must be improved so as to derive more energy from the existing wind and water turbines at prime sites. Such improvements of course must also enable efficient deployment of wind and water turbines at secondary sites, which offer lower mean energy flows. Indeed, initiatives to improve existing wind and water turbines technologies are underway worldwide in a number of public and private programs, many of which are referred to as either “Low Wind Speed” or “Low (Water) Head” technologies.
The development of low wind speed and low water head technologies has been actively encouraged by governments in many countries. For example, in the United States of America, the Department of Energy has established public/private partnerships to encourage development of both types of power generation. Typically, these strategies involve the development of turbines with larger rotors and large installations designed to capture more energy by interacting with a larger portion of the fluid flow.
Recent research and development on low wind speed and low head water turbines, and especially, low wind speed turbines, clearly demonstrates that to-date, improvements have been incremental rather than fundamental. With respect to the development of low wind speed turbines for example, virtually every low wind speed turbine research project is designed to explore the same short list of options, including the following:
(a) development of larger turbines to harvest a larger inflow area;
(b) development of taller towers to carry larger rotor blades and to take advantage of higher wind speed at greater heights;
(c) more efficient combinations of generators, drive train devices and improved power electronics;
(d) development of more flexible turbines and towers, (including hinged blades, flexible configurations and fabrication means, etc.); and,
(e) various approaches which allow operation under highly variable wind conditions such as gusts.
Future research projects are also expected to yield incremental improvements to other technologies used to design, manufacture and control low wind speed turbines. For example, it is anticipated that advanced drive trains, new rotor fabrication techniques, and improvements to low wind speed turbine control and monitoring technology will be developed. These improvements in conjunction with lower costs to assemble very tall, low wind speed turbines on site will lead to increases in the power generation capacity of low wind speed turbines.
It is important to note that virtually all low wind speed turbine research projects have centered on the development of larger turbines capable of producing between 1 and 6 megawatts of electricity. This increase in scale has occurred despite the fact that larger turbine rotors are often less efficient than smaller ones from a cost point of view. The cost of land for sites, aesthetic considerations and the cost of establishing grid connections, maintenance costs and the costs to build access roads, can far exceed any benefit that is derived by the improved power generation capacity of these larger low wind speed turbines. It is also important to note that designing low wind speed turbines with larger turbine rotors suffers other problems aside from being cost inefficient. As the size of turbine blades increase, the turbine towers must grow in both size and strength. Current scales already require tower sections which are near the limit of what can be transported over existing roads and erected on site. Flexible or hinged blades and so-called “soft” (or slightly flexible) towers offer some potential for further growth in the scale of low wind speed turbines but it appears that conventional technology is approaching the upward limits of practical scale.
Similar inherent problems have affected the deployment of larger scale, low water head turbines. Attempts to increase the inflow scale have imposed considerable construction costs and placed practical limits on the number of sites with enough flow to warrant expenditures.
It will be appreciated from the foregoing that there is a need for improvements in wind and water turbine and compressor design, which offer a increased efficiency without significant increases in costs. It is therefore an object of the present invention to provide a novel turbine/compressor.